Changing tabs increments the Synapse at least once you have neurons I think. Sitting in the game tab it does not ever increment lmao.
EDIT: Same thing happens for Neuron's when you have 10 Neural Clusters. Game logic is likely not working as intended? Lack of descriptions make me think this is the point
EDIT 2: I now realize that it is likely a bug/exploit. Once the tier above base is high enough it starts generating in visible time.